[QNN EP] Fix Pad UT (#17982)
### Description
QNN EP has 2 unit tests failing:
TEST_F(QnnHTPBackendTests, DISABLED_PadReflectMode)
TEST_F(QnnHTPBackendTests, DISABLED_Pad4dOutOfRangePadConstantValue)
For the first unit test, in QNN's master definition, it is stated that
when using MIRROR_REFLECT, the before and after pad amounts must not be
greater than shape(in[0])[i] - 1. Therefore, we need to change the pad
amount from {0,2,0,0} to {0,1,0,0}.
For second unit test, QNN does not have limitations stating that pad
constant should be smaller than input[0]. The reason that the test is
failing is because the unit test did not take the pad constant into
consideration when doing quantization.
### Motivation and Context
Fix the 2 unit tests mentioned in description.
